磁性纳米材料Fe3O4-RGO-NH2对Ag+的吸附性能研究

采用一步溶剂热法成功制备了新型磁性纳米吸附剂Fe3O4-RGO-NH2,用透射电子显微镜(TEM)、X射线衍射(XRD)、振动样品磁力计(VSM)及Zeta电势对其形貌及晶型结构进行了表征,研究了Fe3O4-RGO-NH2纳米吸附剂对水溶液中Ag⁺的吸附性能。结果表明,水溶液pH值对Ag⁺吸附具有很大影响,pH=4.0时吸附效果最佳。Ag⁺最大吸附量随着初始浓度及吸附时间的增加而增加,Ag⁺的吸附符合准二级动力学模型。     

Hot corrosion of a novel NiO/NiFe2O4 composite coating thermally converted from the electroplated Ni–Fe alloy

A novel NiO/NiFe₂O₄ composite coating thermally converted from an electroplated Ni–Fe alloy was successfully fabricated. The composite coating consisted of a NiO matrix and homogeneously distributed criss-cross intragranular and intergranular NiFe₂O₄ precipitates, with a very dense and flat structure. The composite, compared to bare Ni metal, exhibited increased hot corrosion resistance under an atmosphere of Na₃AlF₆–AlF₃–CaF molten salts and air at 960 °C, mainly because of the dense structure and well-adhered, homogeneously dispersed intragranular and intergranular NiFe₂O₄ precipitates.     

掺杂FeVO4低温烧结ZnO-Nb2O5-TiO2微波介质陶瓷

研究了FeVO4对ZnO-Nb2O5-TiO2微波介质陶瓷的烧结特性、介电性能、相组成和微观结构的影响.研究表明添加3 ω/%～10ω/%FeVO4可使烧结温度从1200℃降低到960℃,XRD与EDS分析表明FeVO4固溶入主晶相ZnTiNb2O8,导致晶格畸变,缺陷增加,促进传质,在液相和固溶体协同作用下降低烧结温度;随FeVO4添加量的增加,Zn0.15Nb0.3Ti0.55O2相和TiO2相含量增大,介电常数εr基本不变,Q·f值由于晶体缺陷增多和晶粒尺寸不均而下降;FeVO4添加量为4 ω/%的ZnO-Nb2O5-TiO2陶瓷可在940 ℃,2 h条件下致密烧结,微波介电性能为εr=40,Q·f=10 200 GHz(3GHz),τf=-9×10-6/℃,可用于制备各种多层微波频率器件.     

放电等离子高压烧结Sm2Fe17Nx磁体的磁性能和微结构

采用放电等离子烧结技术在1 GPa的高压下制备了Sm2Fe17Nx烧结磁体,并对烧结磁体的微观结构和磁性能进行了分析测试.结果表明,随烧结温度的升高,磁体的致密度显著提高,但Sm:Fe17Nx分解成SmN、a-Fe和N2的程度加剧,造成磁体的矫顽力明显下降.对其分解机制分析发现,其分解过程是一个"易形核、难长大"的过程,分解产物为弥散、细小分布的微晶和非晶的SmN和a-Fe核心.     

Abrasiveness of an electrochemical iron binder on a solid abrasive surface with aluminum oxide particles

The results of the investigation into the abrasiveness of iron-coated surfaces during friction on a solid abrasive surface with aluminum oxide particles on a ceramic binder are presented. It is shown that the particles of the abrasive surface are deteriorated considerably more during friction on a surface of a pure iron coating than on these doped with nickel or cobalt, while they detach from the ceramic binder under considerably smaller loads. It is established that the partial friction coefficient of the abrasive surface is considerably larger during friction on the usual iron depositions than on these doped with nickel or cobalt.     

Special Features of Structure Formation in a Composite Due to Sintering a Mixture of Elementary Powders of Al,Fe and Sn

Metal Science and Heat Treatment - Briquettes of Al – 7% Fe – 38% Sn are obtained by pressing a mixture of elementary powders of aluminum, iron and tin. It is shown that the structure...     

Effect of MnO2 Addition on Sintering Properties of 18NiO-NiFe2O4 Composite Ceramics: Preliminary Results

NiFe₂O₄ samples with small amounts of MnO₂ were prepared via ball-milling process and two-step sintering process from commercial powders. Sintered density, average grain size, and microstructure of Mn-doped 18NiO-NiFe₂O₄ composite ceramics have been investigated by means of x-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. Bending strength was measured by three-point method. The results show that the crystalline structures of the ceramic matrix are still NiFe₂O₄ spinel structure and Mn ions homogeneously distribute in both the grains interiors and the grain boundaries. When 1 wt.% MnO₂ was added, the values of relative density and bending strength of composite ceramics reached their respective maximum of 93.6% and 38.75 MPa, respectively. It is preliminarily found that MnO₂ can reduce the sintering temperature obviously because of partial substitution of Fe³⁺ with Mn⁴⁺ in NiFe₂O₄ lattice.     

Hierarchical porous NiO as a noble-metal-free cocatalyst for enhanced photocatalytic H2 production of nitrogen-deficient g-C3N4

Graphitic carbon nitride with nitrogen vacancies(NV-g-C₃N₄)as a photocatalyst has been studied in solardriven energy conversion.However,expensive and rare noble metal co-catalysts such as Pt or Pd are required in the photocatalytic H₂evolution.Consequently,the exploration of low-cost and high-performance co-catalysts to replace expensive and rare noble metals has received more and more attention.Herein,a novel hierarchical porous NiO anchored on NV-g-C₃N₄is successfully fabricated.The NV-g-C₃N₄/NiO photocatalysts exhibited outstanding H₂evolution rate under visible light irradiation in absence of noble metal cocatalysts.The optimized NV-g-C₃N₄/NiO(the mass ratio of NiO is*1.7%)achieved a maximum H2 evolution rate of 170.60 lmol·g^-1·h^-1,exhibiting*8.3-fold enhancement as compared to that of NV-g-C3N4.NiO as co-catalyst provided more active sites for photocatalytic H2 evolution.Moreover,on the interface of NV-g-C₃N₄/NiO,an interface electric field is formed between NiO and host nitrogen-vacated g-C3N4,facilitating the transfer of the photogenerated electrons from NV-g-C₃N₄to NiO co-catalyst,resulting in significantly promoted migration and separation efficiency of the photogenerated charge carriers.     

Fe_(50-x/2)Al_(50-x/2)Cr_x体系掺杂钨精矿粉激光烧结合金组织及性能研究

以Fe_(50-x/2)Al_(50-x/2)Cr_x(x=4,8,12,16)体系粉末为基体,掺杂1%(质量分数)的钨精矿粉末,压制成坯。利用激光引燃自蔓延烧结制备原位自生颗粒增强复合材料。采用OLYMPUS4000、XRD等微观组织结构表征手段及合金硬度、磨损性能等宏观力学性能及腐蚀性能测试方法,研究不同Cr粉含量对烧结合金组织及性能的影响。结果表明:烧结合金物相主要为Fe_3Al,Al_2O_3,AlCrFe_2,Cr_2O_3及硬质颗粒相W。当Cr含量为8%时,烧结合金内部针状组织细小致密,物相有较好的分散性;磨损率相对较低,为0.38 mg/mm~2。当Cr含量为12%时,烧结合金硬度最高,为11 450 MPa;自腐蚀电位最大,为327.643 mV;腐蚀电流密度最小,为1.044 m A·cm~(-2),腐蚀速率最低。     

Hydraulic design of a grinding wheel with an internal cooling lubricant supply

This paper presents a grinding wheel with an internal cooling lubricant supply (GIC). The cooling lubricant is supplied through channels inside the grinding wheel instead of conventional supply using external nozzles. With the GIC, direct coolant supply into the contact zone is possible. The hydraulic design of the GIC is similar to that of a centrifugal pump impeller. The design process is supported by simulation of fluid dynamics. First tests show that the GIC is able to supply the coolant at different flow rates with cutting speeds up to 60 m/s.     

EuVO4-V2O5复合物作为高性能锂离子电池电极材料

本文采用水热法、阳离子交换法和煅烧处理,制备了相似于梅花结构的EuVO4-V2O5纳米线复合物。分别在300和500 oC温度条件煅烧制备的EuVO4-V2O5纳米线,实验发现随着温度不断增加,EuVO4-V2O5纳米线表面上的纳米颗粒发生了一定的团聚,当温度升高至500 oC时,纳米线出现了融化。通过实验测试比较发现,其中,300 oC煅烧制备的EuVO4-V2O5纳米线复合物的电化学储锂性能较好,在电流密度为30 mA g-1下经过50次循环后的放电比容量仍保持有376 mAh g-1,表现出良好的循环稳定性,且本文开发了一种新的稀土钒酸盐合成路径。     

Formation of Structure and Magnetic Properties in Permanent Magnets Obtained by Pressing and Sintering of Micropowders of Alloy Fe2NiAl with Fusible Additions

Metal Science and Heat Treatment - Results of a study of magnetic properties and structure of specimens of magnets obtained from heat-treated cast alloy Fe2NiAl milled in a planetary mill together...     

Preparation and microstructure characterization of a nano-sized Ti4+-doped AgSnO2 electrical contact material

A Ti4+-doped nano-structured AgSnO2 material was prepared using sol-gel method and characterized by X-ray diffraction (XRD), transmis-sion electron microscopy (TEM), and scanning electron microscopy (SEM). The results show that Ti4+ cations are successfully doped into the crystal lattice of SnO2, and thus significantly improve the electrical conductivity of the sample. Furthermore, the coating of Ag on Ti4+-doped SnO2 nano-sized particles enhances the surface wettability and enables the resulting AgSnO2 material to have better mechanical properties.     

Surface modification of an up-conversion luminescence material by overcoating with SiO2 and its characterization

The surface of an up-conversion luminescence material was modified by overcoating with SiO2, which was syn- thesized from a hydrolysis progress of tetraethoxysilane (TEOS) in alkalescent condition. By analyzing the hydrolyzed mechanism of TEOS, it was found that there was not only physical adsorption but also chemical bonding between the up-conversion material and SiO2. At the same time, some adsorption bands at 1100, 475, 950, and 3500 cm?1 were found by FI-IR, which were the characteristic bands of Si?OH and Si?O?Si. By analyzing the surface elements of the coated material by XPS, it was found that its surface only included Si, O, and C elements, and not F and Y. In the picture of XRD, there was no additional peak after surface modification, suggesting that the silica shell was amorphous. The small peak at 2θ = 23° in the X-ray diffraction pattern of the coated material was caused by the amorphous SiO2 shell, and the TEM image also proved that the surface of the material was successfully modified by overcoating with SiO2. The amount of hydroxyls was then increased on the surface of the material, which made it easy to connect with other active groups.     

Sintering of commercially pure titanium powder with a Nd:YAG laser source

To understand the process of pulsed selective laser sintering, two different energy coupling mechanisms have to be considered. In a first step, the energy is absorbed in a narrow layer of individual powder grains determined by the bulk properties of the material. This leads to a high temperature of the surface of the grains during the interaction. After thermalization of the energy, heat flows mainly towards the center of the grains until a local steady state of the temperature within the powder grain is obtained. Afterwards, the surrounding powder properties have to be considered for the further thermal development. According to these model assumptions, a numerical simulation of the heat flow equation has been performed and compared with experimentally obtained titanium plates, which allowed to obtain a process map.     

Enhanced Magnetostriction of a Narrow Hysteresis Tb0.26Dy0.D4HO0.20Fe2 Alloy

In this work,a magnetic annealing method used to enhance the magnetostrictive property of a narrow hysteresis alloy Tb_0.26Dy_0.54Ho_0.20Fe₂ is reported.Cylindrical-rod shaped specimen with <110> crystal orientation was fabricated using zone-melting unidirectional solidification technique,followed by annealing in a transverse magnetic field of 366 kA/m.The crystal orientation and bi-phase solidified morphology can be retained after magnetic annealing.A high magnetostriction of 1.508×10-3 was obtained in the magnetically annealed specimen,which is 25.2% larger than the untreated one.Simultaneously,the magnetostriction hysteresis width is slightly enlarged from 4.45 to 6.36 kA/m,which is still much lower than that of the Ho-free Tb0.3Dy0.7Fe2 alloy.The additional anisotropy which is induced by magnetic annealing,as reflected by the magnetic hysteresis loops,is responsible for the enhancement of magnetostrictive performance.     

低温烧结B2O3掺杂Y1.05Bi0.75Ca1.2Fe4.4V0.6O12铁氧体的微结构研究

用传统陶瓷工艺制备了0.025wt%B2O3掺杂的Y1.05Bi0.75Ca1.2Fe4.4V0.6O12铁氧体,并对其低温烧结特性进行了研究.结果表明,烧结温度对B2O3掺杂的Y1.05Bi0.75Ca1.2Fe4.4V0.6O12铁氧体的密度影响显著:样品在1040℃烧结,固相反应完全,且具有晶粒大小均匀、结构致密的显微结构.